[clang][bytecode] Allow reinterpret casts from/to the same pointer type (#136692)

Author: tbaederr

clang/lib/AST/ByteCode/Compiler.cpp

@@ -2990,6 +2990,8 @@ bool Compiler<Emitter>::VisitCXXReinterpretCastExpr(
     if (PointeeToT && PointeeFromT) {
       if (isIntegralType(*PointeeFromT) && isIntegralType(*PointeeToT))
         Fatal = false;
+    } else {
+      Fatal = SubExpr->getType().getTypePtr() != E->getType().getTypePtr();
     }
 
     if (!this->emitInvalidCast(CastKind::Reinterpret, Fatal, E))

clang/test/AST/ByteCode/cxx11.cpp

@@ -185,3 +185,11 @@ namespace InitLinkToRVO {
   constexpr A make() { return A {}; }
   static_assert(make().z == 4, "");
 }
+
+namespace DynamicCast {
+  struct S { int x, y; } s;
+  constexpr S* sptr = &s;
+  struct Str {
+    int b : reinterpret_cast<S*>(sptr) == reinterpret_cast<S*>(sptr);
+  };
+}